Reactive Extraction of Butyric Acid from Water Using Trioctyl Amine in 1-Decanol and Green Natural Oils

Abstract

In this work, butyric acid (BA) was extracted using trioctyl amine (TOA). Various temperature-dependent (298.15–318.15 K) process parameters were estimated and analyzed. To reduce the harmful effects of TOA and to avoid the detrimental effects of toxic diluents on microorganisms, green and nontoxic diluents, sunflower and soybean oils, were tested. In physical extraction, KDdil and the partition coefficient, P, decreased in the order of 1-decanol > sunflower oil > soybean oil, whereas the dimerization constant, D, showed the opposite trend. In chemical extraction, the extraction efficiencies were 85–90% for 1-decanol, 82–88% for sunflower oil, and 75–86% for soybean oil. In terms of the distribution coefficient, 1-decanol was a better diluent than sunflower oil, followed by soybean oil. The high distribution coefficients and extraction efficiencies obtained using sunflower and soybean oils were found to be encouraging for their use in biorefinery industries. (KDchem)/(KDphy) was greater than 1.0 in all of the studied cases. The best distribution coefficient model was identified. The complexation reaction stoichiometry and the equilibrium complexation reaction constant were estimated using the differential evolution technique. The order of the complex molality, [HAmSn]org, in different diluents was 1-decanol > sunflower > soybean. Different thermodynamic parameters were determined and analyzed. Variations of acid–extractant, free acid, and dimer molalities at the chemical equilibrium state were found and discussed. Analysis based on the enthalpy change due to mass transfer, (ΔH)mass tr, indicated the easiest mixing of the phases in sunflower oil and the most difficult in soybean oil. The reaction equilibrium constant, KE(m:n), had the highest value at the lowest temperature (298.15 K) and decreased with an increase in temperature and had values in the order of 1-decanol > sunflower > soybean.